JPH0592492A - Method for forming disk substrate - Google Patents

Abstract

(57) [Summary] [Purpose] To form a disc that can be mounted on a disc table with high precision positioning. In a method of forming a disk substrate (11) formed by molding a synthetic resin and having a center hole (12) penetrating in the thickness direction, a connection for closing the center hole (12) inside the center hole (12). After the piece 16 is provided and the disk substrate 11 is molded using the molding die device,
The connecting piece 16 is cut off to form a center hole 12 penetrating therethrough. [Effect] Since the punching process of the center hole is not adopted at the time of molding the disk substrate, burrs and the like are not generated around the center hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a disk substrate formed by molding a synthetic resin forming a disk such as a magneto-optical disk or other optical disk which enables re-recording of information signals.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical disk has been proposed as a disk capable of re-recording information signals. This magneto-optical disk can record information signals such as digitized audio signals with extremely high density. Therefore, the applicant of the present application has proposed a magneto-optical disk having a diameter of 64 mm and capable of recording an audio signal for at least 74 minutes.

As shown in FIG. 5, this magneto-optical disc 1 has a disc substrate 2 formed by molding a resin such as transparent polycarbonate resin, and a signal is provided on one main surface 2a side of the disc substrate 2. It is configured by forming a recording layer. The recording of the information signal on the magneto-optical disk 1 is performed by the light emitted from the optical head on a fine recording track provided on the signal recording layer in a state where the magneto-optical disk 1 is rotated at a predetermined rotation speed. This is performed by irradiating the beam and applying an external magnetic field that is magnetic field modulated according to the information signal to be recorded by the external magnetic field generator.

Since the magneto-optical disk 1 has a small diameter and fine recording tracks are formed at a high density, the magneto-optical disk 1 shown in FIG.
As shown in FIG. 3, the magneto-optical disc 1 is accurately positioned and mounted on the disc table 4 of the disc rotation drive device 3 provided in the recording / reproducing device for rotating the magneto-optical disc 1. It is necessary that the disk table 4 is integrally mounted and rotated in synchronization with the rotation of the disk table 4.

Therefore, the disc table 4 is provided at the center of the disc substrate 2 which constitutes the magneto-optical disc 1.
A center hole 6 is provided for engaging with a centering member 5 for centering the magneto-optical disk 1 mounted on the disk table 4 at the center of rotation. Also,
One main surface 2 on which the signal recording layer of the disk substrate 2 is formed
On the side of the other main surface 2b facing a, a ring-shaped bulge 8 having a mounting reference surface 7 for accurately positioning the mounting height position on the disk table 4 is formed on the center. It is provided so as to surround the hole 6.

A thin metal plate 9 is formed on the main surface 2a side of the disk substrate 2 so as to close the center hole 3.
Are arranged. The metal plate 9 is attracted by a magnet 10 arranged on the disc table 4 side, and the magneto-optical disc 1 mounted on the disc table 4 is integrated with the disc table 4. The center hole 3 is formed so as to penetrate in the thickness direction of the disk substrate 2 so that the magnetic flux of the magnet 10 arranged on the disk table 4 side can be transmitted to the metal plate 9 side.

The magneto-optical disk 1 configured as described above.
6, the center hole 6 is engaged with the centering member 5, the mounting reference surface 7 at the tip end surface of the bulging portion 8 is supported by the disk supporting surface 4a of the disk table 4, and the metal plate 9 Is attracted by the magnet 10 and mounted on the disc table 4, so that the center of the disc table 4 coincides with the center of rotation of the disc table 4, the mounting position is positioned, and the disc table 4 is securely integrated. Can be mounted on.

[0008]

By the way, the disc substrate 2 constituting the magneto-optical disc 1 is formed in a molding cavity formed between a movable mold and a fixed mold constituting a mold device for molding the disc substrate. It is formed by injecting a synthetic resin such as a polycarbonate resin. The center hole 6 with which the centering member 5 engages
Is also formed in the mold device at the same time when the disk substrate 2 is molded.

That is, in the conventional mold apparatus, a punch for advancing and retracting is provided in the molding cavity by a hydraulic mechanism or the like, and a synthetic resin is injected into the molding cavity to mold the disk substrate 2 immediately after. The punching punch is moved to form the center hole 6.

When the punching punch is used to form the center hole 6 in the mold apparatus as described above, there is a problem in that burrs are easily generated in the advancing direction of the punching punch. In particular, the formation of the center hole 6 is performed in a molten state in which the synthetic resin injected into the molding cavity is not completely cured, so that the above-mentioned burr is significantly generated.

As shown in FIG. 7, when such burrs 2c are generated on the inner peripheral surface 6a of the center hole 6 with which the centering member 5 engages and on the mounting reference surface 7 at the tip of the bulging portion 8,
The accuracy of the center hole 6 deteriorates and the smoothing of the mounting reference surface 7 is hindered. As a result, the magneto-optical disk 1 cannot be accurately centered and accurately positioned, and cannot be mounted on the disk table 4.

Therefore, burrs generated when the center hole 6 is formed by using the punching punch arranged in the die apparatus are
It can be considered to generate the magneto-optical disk 1 at a position that does not affect the mounting of the magneto-optical disk 1 on the disk table 4. For example, the punching direction of the center hole 6 by the punching punch is from the other main surface 2b side of the disk substrate 2 on which the centering member 5 is engaged to the one main surface 2a side where the signal recording layer is formed. It can be considered as a direction.

By the way, the disc substrate 2 constituting the magneto-optical disc 1 has one main surface 2 on which a signal recording layer is formed.
Prepits and the like that form the recording track are formed in a. Therefore, a stamper is arranged on the side of the molding cavity on which the one main surface 2a is formed.

As described above, when the punching direction of the center hole 6 by the punching punch is set to the direction from the other main surface side 2b of the disk substrate 2 to the one main surface 2a side, the punching punch is stamped. Will be disposed on the side opposite to the side on which is disposed.

Therefore, when the stamper is arranged on the movable mold side of the mold device, the punching punch is arranged on the fixed mold side. A sprue bush for injecting molten resin for molding is also provided on the fixed mold side. Therefore, if a punching punch that can be advanced and retracted is provided in addition to this sprue bush, the sprue bush can be attached. Not only the structure and the structure of the injection molding machine are complicated, but also the mold apparatus is complicated.

Contrary to the above construction, if the stamper is arranged on the fixed mold side of the mold device and the punching punch is arranged on the movable mold side, the stamper is fixed on the fixed mold side. Since the mechanism for supporting the resin and the resin inflow port through which the molten resin is injected are arranged close to each other, the structure of the mold device becomes complicated. Furthermore, the structure of the movable mold side becomes complicated, which makes it difficult to design and process the mold device.

Therefore, the present invention is intended to provide a forming method which enables formation of a center hole without generating burrs and the like, and enables formation of a disk substrate with high accuracy. Further, the method of the present invention enables the formation of the center hole without using a punch for punching that is arranged so as to be able to move forward and backward in the mold device, and simplifies the mold device for molding a disk substrate. It is proposed for the purpose of facilitating the design and processing of the mold device.

[0018]

The present invention provides a method of forming a disk substrate, which is formed by molding a synthetic resin and has a center hole penetrating in the thickness direction.
A connecting piece for closing the center hole is provided inside the center hole, the disk substrate is molded by using a molding die device, and then the connecting piece is cut off to form a center hole penetrating therethrough. This achieves the above object.

[0019]

According to the method of the present invention, a connecting piece for closing the center hole is provided on the inner side of the center hole, the disk substrate is formed by using a molding die, and then the connecting piece is cut off to penetrate the center hole. Since it is formed, it is not necessary to provide a punching punch or the like for forming the center hole in the mold device for molding the disc substrate.

Further, the connecting piece provided inside the center hole is removed by punching or cutting.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A disk substrate forming method according to the present invention will be described below in the order of steps with reference to the drawings. In the method according to the present invention, first, a disk substrate 11 having a disk shape as shown in FIG. 1 is molded using a mold device for molding a disk substrate. The disc substrate 11 is formed by molding, for example, a transparent polycarbonate resin having a good light-transmitting property, and one main surface 11a is coated with a magneto-optical recording medium constituting a magneto-optical disc. A layer is formed. On one main surface 11a side on which the signal recording layer is formed, prepits forming a recording track are formed by a stamper arranged in the mold device at the same time when the disk substrate 11 is molded.

Further, one main surface 11a of the disk substrate 11 on which the signal recording layer is formed and the other main surface 1 opposite to the main surface 1a.
When configured as a magneto-optical disk, the 1b side serves as a signal reading surface on which the light beam emitted from the optical head is irradiated.

A center hole 12 is formed at the center of the disc substrate 11. The center hole 12 engages with the centering member 5 arranged at the center of rotation of the disk table 4, like the center hole provided in the disk substrate.

Further, the other main surface 1 of the disk substrate 11 opposite to the one main surface 11a on which the signal recording layer is formed.
On the side of 1b, a ring-shaped bulging portion 14 having a mounting reference surface 13 for accurately positioning the mounting height position on the disc table 4 is formed on the tip end surface so as to surround the center hole 12. Has been done.

Further, one main surface 1 of the disk substrate 11
When a magneto-optical disk is constructed by using the disk substrate 11, the metal plate mounting recess 15 is provided so that the metal plate is attracted by the magnet 10 arranged on the disk table 4 side and fitted to the metal plate 1a. Are provided so as to surround the center hole 12.

The disk substrate 11 used in the method of the present invention is integrally provided with a connecting piece 16 located inside the center hole 12 and closing the center hole 12. The connecting piece 16 is formed at a position deeper than the depth of penetration of the centering member 5 arranged on the disc table 4 into the center hole 12, that is, at a position deviated to one main surface 11a side.

The disk substrate 11 configured as described above
Is molded using the molding die device 20 configured as shown in FIG. This mold device 20 includes a fixed mold 21.
And a movable mold 22, and a molding cavity 23 for molding the disk substrate 11 is defined between the fixed mold 21 and the movable mold 22.

A sprue bush 24, which is located at the center of the molding cavity 23 and allows the molten polycarbonate resin supplied from the injection molding machine to flow into the molding cavity 23, is disposed on the fixed mold 21 side. It is set up. And the melted polycarbonate resin is
The resin is introduced into the molding cavity 23 through a resin inlet 25 formed in the sprue bush 24.

The tip end side of the sprue bush 24 is formed in a shape corresponding to a part of the center hole 12 on the one main surface 11a side and the metal plate mounting recess 15.

A stamper 26 for molding prepits forming recording tracks is provided on the surface of the fixed mold 21 on the side forming the molding cavity 23. The stamper 26 is attached to the fixed mold 21 while being supported by stamper retainers 27 and 28 on the inner peripheral side and the outer peripheral side, respectively. The inner peripheral side stamper retainer 27 that supports the inner peripheral side of the stamper 26 is fitted and attached to the stamper retainer support body 29 that is fitted and disposed in the sprue bush 24, and supports the outer peripheral side of the stamper 26. The outer peripheral stamper retainer 28 is fitted and attached to the outer peripheral side of the fixed mold 21.

On the other hand, the movable mold 22 disposed so as to face the fixed mold 21 has a cylindrical bulge for forming a ring-shaped bulge 14 having a mounting reference surface 13 at the tip end surface thereof. A part forming insert 30 is provided. A center hole forming insert 31 for forming a part of the center hole 12 located on the other main surface 11b side is provided on the inner peripheral side of the bulging part forming insert 30. Then, the bulging part forming insert 30 and the center hole forming insert 31 are
It is arranged integrally with the movable mold 22. Therefore, when the movable mold 22 is separated from the fixed mold 21 side after the disk substrate 11 is molded, the movable mold 22 is moved integrally with the movable mold 22.

The disk substrate 11 molded as shown in FIG. 1 by using the mold apparatus 20 as described above is taken out from the molding cavity 23, and then, as shown in FIG. The connection piece 16 in the state where the hole 12 is closed is cut off. The cutting of the connecting piece 16 is not limited to the punching machine 32, and may be performed using a cutting blade 33 or the like as shown in FIG. When the connecting piece 16 is cut off using the cutting blade 33, the center hole 1
The inner peripheral surface 12a of 2 can be a smooth surface with extremely high precision.

By cutting the connecting piece 16 in this manner, the disk substrate 11 having the center hole 12 penetrating in the thickness direction is completed.

Although the method of forming the disk substrate applied to the magneto-optical disk has been described in the above-mentioned embodiment, the method of the present invention has the center hole and the main surface of the disk substrate is connected to the disk table. It can be widely applied to disks having a mounting reference surface and a centering surface for the disk table.

[0035]

As described above, since the method of the present invention does not employ the punching process of the center hole when molding the disc substrate, the disc substrate can be highly accurately formed without generating burrs around the center hole. Can be formed. Then, the disc configured by using this disc substrate can be accurately positioned and mounted on the disc table.

Further, according to the method of the present invention, the center hole can be formed without using the punch for punching which is arranged in the mold device so as to be able to move forward and backward. Therefore, the mold device for molding the disk substrate can be simplified. Is achieved, which facilitates the design and processing of the mold device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a disk substrate applied to the method of the present invention.

FIG. 2 is a cross-sectional view of a mold device for molding a disk substrate applied to the method of the present invention.

FIG. 3 is a cross-sectional view showing a state in which a connecting plate that closes a center hole of a disc substrate is cut off.

FIG. 4 is a cross-sectional view showing another example of a state in which the connecting plate that closes the center hole of the disc substrate is cut away.

FIG. 5 is a partially cutaway perspective view of a conventional magneto-optical disk.

FIG. 6 is a sectional view showing a state in which a conventional magneto-optical disk is mounted on a disk table.

FIG. 7 is a partial cross-sectional view showing an enlarged part around a center hole of a conventional magneto-optical disk.

[Explanation of symbols]

 11 Disk Substrate 12 Center Hole 16 Connecting Piece 20 Mold Device 21 Fixed Mold 22 Movable Mold 23 Molding Cavity

Claims (1)

[Claims] 1. A method for forming a disk substrate, which is formed by molding a synthetic resin and has a center hole penetrating in the thickness direction, wherein a connecting piece for closing the center hole is provided inside the center hole. A method for forming a disk substrate, which comprises providing a disk substrate using a molding die device and then cutting the connecting piece to form a center hole therethrough.